Method of manufacturing a light emitting diode unit body

ABSTRACT

Method of fabricating LED assembly disclosed herein can provides a string of original colored high intensity LEDS usable for screen displaying or traffic signal lights molded by injecting harmless polyacrylic resin in a short time duration and at low temperature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to method of fabricating LED assembly, andmore particularly, to method of fabricating a string of original colored(E,G,B) high intensity LEDS (Light Emitting Diodes) to be displayed on ascreen or used as a traffic light source.

2. Description of the Prior Art

In conventional method of fabricating LED assembly, an epoxy resin addedwith a hardener molded by baking at high temperature (90° C.˜110° C.) isa commonly adopted procedure. For example, in a cited case herein, whichwas patented by NO3 11269 in Taiwan, a fabrication method by plasticpackaging was employed. The material used for fabrication was a plasticresin (an hardener was required to cure its softness at roomtemperature) applied to the micro structure of a semiconductor surfaceby coating or spraying, them the later fabricating steps weresuccessively carried out after hardening of the plastic resin. As thepackage was performed by coating or spraying, the finished surface ofthe product was somewhat uneven. In addition, such a fabrication methodprovided by the cited case is only applicable for semiconductorpackaging owing to the fact that it is unable to withstand ejectingpressure higher than 40 psi.

Since high intensity blue colored LED has come to practical use, it soonbecomes a favorite of multi-media world. Further innovation on precisionof light emission angle and uniformity in tint are asked that can not beattained with a conventional resin treatment.

Filling epoxy resin or silicone rubber in a LED assembly housing byheating at a temperature above 120° C. in an oven, the rate of yieldscarcely exceeds 90% with disqualified results in disorganized disposalof elements, inadequate quantity of resin attachment, and unevenness ofsurface. Besides, a cracked resin package is not repairable andinadvertent spattering of resin in the front of surface an unit LEDcauses degrading of brightness.

High intensity blue or green LED lighting source should be reliably madewatertight if it is to be installed outdoor. However, such an aim ishard to be attained by a conventional method of driving in an oven afterinstilling a resin with a low cost.

In order to overcome the shortcomings inherent to the conventionaltechnique described above, the present inventor has delved into thismatter with a long time efforts and came to realization of the presentinvention.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide method offabricating LED assembly by using polyacrylic resin as a essentialpackaging material and applying a pressure above 40 psi to integrallyform a watertight contour of a string of LED assembly by injectionmolding process so as to obtain a good looking, smooth surfacedappearance of the product.

It is another object of the present invention to provide method offabricating LED assembly by using an innovative plastic resin injectionmachine to save 50% time needed in the whole stages of fabrication so asto minimize production cost internationally competitive with otherleading countries in this field of technology.

In the method of the present invention, the time duration required forpolyacrylic resin injection per round is only about 40 sec withtemperature descending from 110° C. down to below 60° C. fully incompliance with internationally standardized LED fabricationspecification and increase of 130 times production speed compared withgeneral conventional method of fabrication. Besides, in case the housingof the LED assembly is cracked, it is 99% repairable by fusing plasticresin of the housing.

To enable a further understanding of the innovative and technologicalcontent of the invention herein, refer to the detailed description ofthe invention and the accompanying brief description of the drawingsappended below. Furthermore, the attached drawings are provided forpurposes of reference and explanation, and shall not be construed aslimitations applicable to the invention herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings disclosed two illustrative embodiments of the presentinvention which serve to exemplify the various advantages and objectshereof, and as follows:

FIG. 1 is a view illustrating the first step of method of fabricatingLED assembly according to the present invention;

FIG. 2 is a view illustrating the second step of method of fabricatingLED assembly according to the present invention;

FIG. 3 is a view illustrating the third step of method of fabricatingLED assembly according to the present invention;

FIG. 4 is a view illustrating the fourth step of method of fabricatingLED assembly according to the present invention;

FIG. 5 is a view illustrating the fifth step of method of fabricatingLED assembly according to the present invention;

FIG. 6A is a fragmentary cross sectional view of a conventional LEDassembly;

FIG. 6B is another fragmentary cross sectional view of a conventionalLED assembly;

FIG. 7 is a view of method of fabricating LED Assembly in anotherembodiment of the present invention;

FIG. 8 is a view illustrating the first step of method of fabricatingLED assembly in another embodiment of the present invention;

FIG. 9 is a view illustrating the second step of method of fabricatingLED assembly in another embodiment of the present invention;

FIG. 10 is a view illustrating the third step of method of fabricatingLED assembly in another embodiment of the present invention;

FIG. 11 is a view illustrating the fourth step of method of fabricatingLED assembly in another embodiment of the present invention; and

Table 1 is a comparison between properties of polyacrylic resin andepoxy resin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the method of fabricating LED assembly of the present invention shownin FIG. 1 at first step, a plurality of unit LEDS 10 welded onto anelectrical board 11 which has been already cut into a desired shape,then lead conductors 12 are welded to the electrical board 11 at aproper position. The unit LEDS are disposed according to a definite wayso as to exhibit a lustrous and beautiful high quality mixed color lateron.

In the second step shown in FIG. 2, the string of LEDS 10 buried in aframed gutter 13 and fixed therein, the gutter 13 shall be well fittedfor the unit LEDS 10 in every respect such that the resin to be injectedthereinto in the next step will not overflow thereby ensuring a goodproduct quality.

In the third step shown in FIG. 3, the framed gutter 13 together withthe LED assembly 10 is put in a mold cavity of a mold 14 which is to beclosed both from right and left, and the LED assembly 10 is settledthereat.

In the fourth step shown in FIG. 4 polyacrylic resin 16 is injected intothe framed gutter 13 from an injection port 15, and a copper stick 17 issimultaneously inserted thereinto to stabilized the injection operation.It should be noted that an annular groove 18 will be formed at the rearpart of the injected polyacrylic resin 16. However, a rubber ring 19(not shown) can be filled therein for preventing entry of water drips ina rainy day so as to protect the product from defection.

In the fifth step shown in FIG. 5, a finished product of LED assembly 21is taken out from the mold 14 thus completing the whole fabricationsteps. In the present invention, the time required for polyacrylic resin16 injection per round is only about 30 sec. with temperature descendingfrom 90° C. down to below 60° C. fully in compliance withinternationally standardized LED fabrication specification, and the rateof yield attains as high as 99%.

For comparison, in a conventional fabrication method using epoxy resinor silicone rubber as a packaging material, and heating in an oven at atemperature above 120°, the rate of yield obtainable is below 90%accompanying with dissatisfactory structure of resin package, andunsmoothness of the finished product.

For a further comparison between the product fabricated according to aconvention method and that according to the present invention, referenceshould be made to FIGS. 6A and 6B. As shown in FIG. 6A, the productmolded with epoxy resin or silicone rubber is finished in such a statethat the surface between adjacent unit LEDS is formed in an arcuate FIG.22, an incident light 23 (from a lamp source or sun light) is reflectedin diffusing state lacking uniformity in brightness and homogeneity incolor. On the contrary, the fabrication method according to the presentinvention is employed in FIG. 6B wherein the product is molded withpolyacrylic resin by injection process lasting for approximately 30 secat a temperature descending from 90° C. to below 60° C. It should benoted that the product fabricated in a withstandable temperature andtime duration has a resultant planar surface 24 between adjacent unitLEDS which acts as a reflecting mirror against an incident light (from alamp source or sun light) so that there are no shortcomings as that ofthe product fabricated according to the conventional techniques.

FIG. 7 shows a view of method of fabricating LED assembly in anotherembodiment of the present invention. As shown in FIG. 7 this LEDassembly is applicable as a traffic signal lamp for cross roads. It ischaracterized in that the LED assembly 25 containing red, green andyellow colors is screwed onto a screw socket 27 without using anyluminary but only adding a light shade 26. With this construction, bythe aid of direct emission property of LED light, the light signal ofone of the cross road at the instant of variation from yellow to red isnot visible from the driver waiting at the other cross road so as toevade his/her too early starting thereby eliminating a possible trafficaccident as that is apt to happen in case a conventional traffic signallamp in a non-shaded luminary is installed on a cross road intersection.

In the first step of fabrication in another embodiment shown in FIG. 8,a plurality of unit LEDS 30 is welded onto an electrical circuit board31 which has been already cut into a desired shape.

FIG. 9 shows the second step of method of fabricating LED assembly inanother embodiment of the present invention, it differs from the stepshown in FIG. 1 That lead conductors 32 are not connected to a circuitboard 31 in advance, but are passed through the guide hole 33 in apreformed housing before connecting to the circuit board 31. Afterwardthe circuit board 31 is pushed and engaged to an inner flange 34 of thehousing to be fixed thereof, and then the LED assembly is buried in aframed gutter 35.

FIG. 10 shows the third step of method of fabricating LED assembly inanother embodiment of the present invention, the framed gutter 35together with the LED assembly is settled in a mold 36, in this case asthe inner part of the framed gutter 35 is divided in two spacing by thecircuit board 31, a front room 37 a and a rear room 37 b, so that theresin has to be injected thereinto through respective inlet ports 38 aand 38 b.

FIG. 11 shown the forth step of method of fabricating LED assembly inanother embodiment of the present invention, wherein a finished LEDassembly 39 is taken out of the mold cavity after carrying out injectionmolding about 30 sec. from 90° C. to 60° C. with 99% rate of yield.

Table 1 is a comparison between properties of polyacrylic resin employedin the present invention and epoxy resin employed in prior techniques.

TABLE 1 Epoxy Polyacrylic resin State (liquid plastic) (solid state) Wayof finishing Adding hardener Heating up to 200° C. and anti-ultra violetray substance Objects to be packaged LED chip, IC chip Integrated LED,entirely water-proof IC Way of filling Coating, spraying, Squeezing byinjection implanting Injection pressure Almost nil if by Applyingcoating or 15 kgf-30 kgf high implanting pressure to squeeze into moldWay of hardening  85° C. for 4 hours; 155° C. for 10 sec 100° C. for 2hours after placed in mold Available waiting time  25° C. for 4 hours;No time limit  40° C. for 5 hours (in any environmental after mixingcondition) Heat deformation 122° C. 135° C. occurring temperatureCombustion Combustible Non-combustible UL94 Dielectric constant 3.12 at1 KHz 3.09 at 1000 KHz Volumetric resistance 1.3 × 100,000 1,000,000,000Ohm-cm Ohm-cm and up Arc withstanding ability none 130 sec Hardness 114R-Scal 90 R-Scal Boiled water 0.42% for 1 hour 0.02% for 1 hour,absorption rate (0% at 23° C.) (0% at 23° C.) Temperature expansion 6.0× (−100,000) 6.0 × (−100,000) coefficient

In all, after having made careful consideration over the above detaileddescription of the present invention, it will be clearly understood thatthe present invention has several noteworthy features which areprominently superior to any conventional techniques, and are as follows:

1. The product has good appearance, smooth contour surfaces due toadequate resin attachment, well-organized disposal of componentsexcellent water tightness and low production cost with nearly 100% rateof yield.

2. A noteworthy contribution to environmental protection that generationof poisonous gas due to heating resin material at high temperature for along time that is the problem, inherent to conventional methods iseliminated because harmless polyacrylic resin is used with a very shorttime duration of heating under relatively low temperature in the presentinvention.

Those who are skilled in the art will readily perceive how to modify theinvention. Therefore the appended claims are to be construed to coverall equivalent structures which fall within the true scope and spirit ofthe invention.

What is claimed is:
 1. Method of fabricating LED assembly comprisingfive steps: disposing and welding a plurality of unit LEDS onto an readycut electrical circuit board, and connecting with lead conductors;burying said LEDS assembled in the precedent step in a framed gutterfixedly, and exposing appropriately portions for injecting polyacrylicresin; setting said framed gutter together with said LED assembly into amold cavity; simultaneously inserting a copper stick into said mold, andinjecting polyacrylic resin into said mold cavity after closing saidmold cavity; and picking up the finished injection molded LED assemblyout of said mold.
 2. The method of claim 1, wherein said LED assembly isable to made into a monocolored light source to be used as a lamp bulb.3. The method of claim 1, wherein a contour of a housing said LEDassembly is able to be formed into various kinds of polyhedronsaccording to configuration of said mold.